1. Field of the Invention
This invention relates to a novel method of manufacturing target shooting capsules. It further relates to novel forms of target shooting capsules now made possible by this method of manufacture. These target shooting capsules are to be fired by air powered rifles or handguns in various recreational sports.
2. Description of Related Art
In recent years, a series of recreational sports has grown up around the use of air powered guns firing target capsules comprised of soft gelatin envelopes filled with non-toxic, washable liquid dyes. These capsules are referred to as "paintballs". The use of paintballs varies from target shooting to teams of people playing "Capture the Flag", to various pseudo and actual military training scenarios. By firing balls which break on impact and leave a stain, target impact may be determined in a safe and non-destructive fashion. In a large scale game it is not uncommon for one quarter million balls to be fired. Accordingly, one of the considerations is that the capsules and their fill must be inexpensive and readily biodegradable. The capsules must be sturdy enough to survive the stresses of being handled, carried and fired, but be fragile enough to break upon impact without causing bodily harm.
All paintballs known to the applicants are formed from the same process based upon the R. P. Sherer developed rotary die process for manufacturing soft elastic gelatin capsules. In this process flat sheets of heated gelatin are brought together in the center of a rotary die cutter/press. The dies cut out two circular patches of gelatin which are pressed together around the edges at a temperature which keeps them elastic while the resulting circular envelope is injected with liquid fill material under pressure. As the envelope fills, it is pressed against a forming cavity on the roller which gives it its final approximate shape. The injection-opening is sealed and the now assembled capsules are ejected and washed.
The original, and still predominant, use for the filled gelatin capsule process is to create pharmaceutical capsules for delivering liquid pharmaceuticals for internal use. Paintballs are manufactured on the identical equipment, and patents relating to paintballs have been issued relating to the fill contents and small modifications to the gelatin shell formulation, but not to the basic manufacturing process.
Paintballs produced by this process have certain characteristic problems. The pharmaceutical process is more concerned with the application of precise doses of fill material than with dimensional stability. The soft and elastic gelatin of the shells tends to be of a deformed shape. This problem is aggravated by the manufacturing stresses generated when two essentially flat sheets of gelatin are formed into an approximate spherical shape by fill pressure. For good aerodynamic flight characteristics, it is required that the capsules be as nearly spherical as possible. A large proportion of paintballs must be rejected at the manufacturer in order to deliver spherical paintballs. Further, the elastic gelatin is very susceptible to softening under elevated environmental temperature and humidity, which can aggravate any irregularities. Additionally, the elastic covering is comparatively susceptible to damage, causing jamming in feeding mechanisms and gun barrels. Additionally, because of the dimensional inaccuracy of the capsules, the air powered guns must be manufactured to accommodate out of round paintballs without jamming, which results in a slight but significant loss of efficiency in use of the portable compressed air containers employed to power paintball guns. Finally, soft elastic coatings can not support certain shapes that would improve the accuracy of target shooting capsules.
A second type of gelatin pharmaceutical capsule, in which two halves of a capsule are formed by dipping forms into a gelatin solution and then are assembled together with a fill material, is not suitable for use with liquid fills.
Very recently, an entirely new form of bio-degradable substance has been created by Warner-Lambert Company of Morris Plains, N.J. In U.S. Pat. No. 4,738,724 they describe a method for manufacturing pharmaceutical capsules using injection molding of starch based compounds.